Folded dipole antenna on hemispherical PMC shell for helmet antenna design

For the disaster prevention, the person has to wear the helmet and use the transceiver by one hand operation. The helmet antenna has been required to achieve the hands-free operation. Since the operational band for disaster prevention is 150 MHz, which corresponds to wavelength of 2 meters, the required performances for the helmet antenna are not only the low-profile and small configuration but also the suppression of the radiation toward a human head. This paper presents the folded dipole antenna on the hemispherical PMC shell for the helmet antenna design. By applying the perfect magnetic conductor (PMC) boundary to the surface of the hemispherical shell, the suppression of radiation toward the human head and impedance matching can be achieved simultaneously.